A mole (abbreviated mol) is a standard scientific number for measuring quantities of small particles such as atoms, compounds, molecules, formula units, etc. One mole equals 6.02 x 10 ^ 23 particles. This is the number of atoms that is determined scientifically to be found in 12 grams of carbon- 12 (which was chosen as the reference standard by the International System of Units).
We can write particles per mole as two different conversion factos:
6.02 x 10 ^ 23 particles/ 1 mole
1 mole / 6.02 x 10 ^ 23 particles.
If given the number of particles and asked to find the number of equivalent moles, as is asked in your question above, then the problem would be set up using stoichiometry as such:
# of given particles x (1 mole/ 6.02 x 10 ^ 23 particles) = # of equivalent moles